Electro-magnetic radiation such as x-ray radiation, when passing through matter, experiences three types of disturbances: there is absorption, there is refraction (that is, the phase of the radiation wave front experiences a shift) and there is a type of scattering, also called “small angle scattering”.
Traditional radiography focused solely on the absorption disturbances. Recently, differential phase contrast techniques and related imagers have been devised that allow imaging all three of those disturbances and capture respective contrasts in separate images. The phase contrast image affords soft tissue discrimination superior to traditional, solely absorption based imagery. It has been observed also that despite the excellent imaging prospects the uptake, especially in the medical fields, have been not as enthusiastic as one may have expected. One reason for this may be that calibration procedures prove rather cumbersome for differential phase contrast imaging system because of required interferometric equipment (essentially a plurality of gratings). Some calibration procedures are based on so called “phantoms” such as described in US 2011/0243305.